[IPv4] Fix multicast address checking

From: Viswanath Krishnamurthy <viswa.krish@gmail.com>

The current ipv4 incorrectly checks the IP address for multicast address.
This causes valid IPv4 unicast address to be trated as multicast address

For e.g if the PXE/tftp server IP address is 192.168.4.XXX where XXX is
224 or greater, it gets treated as multicast address and a ethernet
multicast address is sent out on the wire causing timeouts

src/net/ipv4.c

 		memcpy ( ll_dest, ll_protocol->ll_broadcast,
 			 ll_protocol->ll_addr_len );
 		return 0;
-	} else if ( IN_MULTICAST ( dest.s_addr ) ) {
+	} else if ( IN_MULTICAST ( ntohl ( dest.s_addr ) ) ) {
 		/* Special case: IPv4 multicast over Ethernet.	This
 		 * code may need to be generalised once we find out
 		 * what happens for other link layers.